Polylactic acid composition

Abstract

It is an object of the present invention to provide a composition comprising polylactic acid and having improved injection moldability and an injection molded product thereof. The object of the present invention is attained by a specific polylactic acid composition which meets the following requirements (a) to (g) at the same time: (a) it must have a weight average molecular weight of 70,000 to 700,000; (b) the total content of Sn atom, Ti atom, Al atom and Ca atom must be 3 to 20 ppm; (c) it must contain a P atom in an amount of 3 to 3,000 ppm; (d) the (total number of gram-atoms of Sn, Ti, Al and Ca)/(number of gram-atoms of P) value must be 0.01 to 5; (e) the content of a compound having a molecular weight of 150 or less must be not more than 0.2 wt %; (f) the COOH terminal group concentration must be not more than 30 equivalents/ton; and (g) the melt viscosity (P) at a melting temperature of 230° C. must satisfy the following expression (1): 10 Pa·s< P <100 Pa·s  (1).

1 . A polylactic acid composition which comprises:
 (A) 30 to 70 parts by weight of polylactic acid (A) comprising not less than 90 mol % of an L-lactic acid unit and less than 10 mol % of a D-lactic acid unit and/or a comonomer unit except for lactic acid; and   (B) 70 to 30 parts by weight of polylactic acid (B) comprising not less than 90 mol % of a D-lactic acid unit and less than 10 mol % of an L-lactic acid unit and/or a comonomer unit except for lactic acid,   
     and which meets the following requirements (a) to (g) at the same time:
 (a) it must have a weight average molecular weight of 70,000 to 700,000; 
 (b) the total content of Sn atom, Ti atom, Al atom and Ca atom must be 3 to 3,000 ppm; 
 (c) it must contain a P atom in an amount of 0.01 to 3,000 ppm; 
 (d) the (total number of gram-atoms of Sn, Ti, Al and Ca)/(number of gram-atoms of P) value must be 0.01 to 5; 
 (e) the content of a compound having a molecular weight of 150 or less must be not more than 0.2 wt %; 
 (f) the COOH terminal group concentration must be not more than 30 equivalents/ton; and 
 (g) the melt viscosity (P) at a melting temperature of 230° C. must satisfy the following expression (1):
   10 Pa·s< P <100 Pa·s  (1). 
 
 
   
   
       2 . An injection molded product which comprises:
 (A) 30 to 70 parts by weight of polylactic acid (A) comprising not less than 90 mol % of an L-lactic acid unit and less than 10 mol % of a D-lactic acid unit and/or a comonomer unit except for lactic acid; and   (B) 70 to 30 parts by weight of polylactic acid (B) comprising not less than 90 mol % of a D-lactic acid unit and less than 10 mol % of an L-lactic acid unit and/or a comonomer unit except for lactic acid,   
     and which meets the following requirements (a) to (g) at the same time:
 (a) it must have a weight average molecular weight of 100,000 to 500,000; 
 (b) the total content of Sn atom, Ti atom, Al atom and Ca atom must be 5 to 300 ppm; 
 (c) it must contain a P atom in an amount of 20 to 5,000 ppm; 
 (d) the (total number of gram-atoms of Sn, Ti, Al and Ca)/(number of gram-atoms of P) value must be 0.01 to 5; 
 (e) the content of a compound having a molecular weight of 150 or less must be not more than 0.1 wt %; 
 (f) the COOH terminal group concentration must be not more than 30 equivalents/ton; and 
 (g) the melt viscosity (P) at a melting temperature of 230° C. must satisfy the following expression (1):
   10 Pa·s< P <100 Pa·s  (1). 
 
 
   
   
       3 . The molded product according to  claim 2 , wherein the poly-L-lactic acid unit and the poly-D-lactic acid unit form a stereocomplex crystal in the injection molded product.